New Project: The nematode, Caenorhabditis elegans, is one of the most studied model organisms in biological sciences and is especially prized for its excellent genetics and the numerous detailed studies of development and its state-of-the-art bioinformatics. Ecological studies have, sadly, been almost lacking. The recent discovery that C. elegans and other Caenorhabditis species are commensal with snails and other invertebrates has made the collection of these species in the wild much more reliable. In the last funding period these finding were extended and numerous wild isolated of Caenorhabditis sp. have been isolated from the wild. We propose in to build upon these earlier studies and to use modern technology to study these isolates with regard to evolutionary, molecular, physiological, and genetic parameters, with a specific focus on the role that environmental variation plays in mediating an individual's response to stress and its eventual effects on longevity. Aim 1. Characterize genomic and demographic variation from worldwide collections of C. elegans natural populations. Aim 2. Characterize the natural microbial environment experienced by C. elegans and test whether this environment alters individual demography and lifespan in a genotype-specific manner. Aim 3. Test the theory that variation in lifespan is mediated by a trade-off between stress resistance and reproduction by examining the role that the dauer stage plays in mediating the demographic response to environmental perturbation. Aim 4. Examine the role that extended postreproductive longevity plays within natural populations using mark-recapture methods within controlled macrocosms. RELEVANCE (Seeinstructions): This new project to this Program proposal will use a well-studied model organism to further explore, examine, and inform lifespan and aging in other species and in humans, especially the role that environment plays in mediating an individuals response to stress and its eventual effects on longevity.